Pulsed Laser Evaporation Research Articles

Deposition of matrix-free fullerene films with improved morphology by matrix-assisted pulsed laser evaporation (MAPLE)

Thin films of C60 were deposited by matrix-assisted pulsed laser evaporation (MAPLE) from a frozen target of anisole with 0.67wt% C60. Above a fluence of 1.5J/cm2 the C60 films are strongly non-uniform and are resulting from transfer of matrix-droplets containing fullerenes. At low fluence the fullerene molecules in the films are intact, the surface morphology is substantially improved and there are no measurable traces of the matrix molecules in the film. This may indicate a regime of dominant evaporation at low fluence which merges into the MAPLE regime of liquid ejection of the host matrix at higher fluence.

Functionalized antibiofilm thin coatings based on PLA–PVA microspheres loaded with usnic acid natural compounds fabricated by MAPLE

We report the fabrication of thin coatings of PLA–PVA microspheres loaded with usnic acid by matrix assisted pulsed laser evaporation (MAPLE) onto Ti substrate. The obtained coatings have been physico-chemically characterized by scanning electron microscopy (SEM) and infrared microscopy (IRM). In vitro biological assays have been performed in order to evaluate the influence of fabricated microsphere thin coatings on the Staphylococcus aureus biofilm development as well as their biocompatibility. SEM micrographs have revealed a uniform morphology of thin coatings, while IRM investigations have proved both the homogeneity and functional groups integrity of prepared thin coatings. The obtained microsphere-based thin coatings have proved to be efficient vehicles for usnic acid natural compound with antibiofilm activity, as demonstrated by the inhibitory activity on S. aureus mature biofilm development, opening new perspectives for the prevention and therapy associated to biofilm related infections.

Tuning the Refractive Index of Homopolymer Blends by Controlling Nanoscale Domain Size via RIR‐MAPLE Deposition

Anti‐reflection (AR) coatings designed for glass and other rigid, inorganic substrates are commercially available; however, these inorganic AR coatings tend to crack or delaminate on flexible substrates. A polymeric film with a gradient refractive index (GRIN) profile would make an ideal AR coating for flexible substrates, but such coatings are challenging to fabricate using traditional, solution‐based techniques. Emulsion‐based resonant infrared, matrix‐assisted pulsed laser evaporation (RIR‐MAPLE) offers a straightforward approach to enabling the desired GRIN profile in polymeric materials. Two homopolymers (polystyrene (PS) and poly(methyl methacrylate) (PMMA)) are deposited as a blend and one component (PMMA) is dissolved, leaving behind a porous PS film. The porosity and refractive index (RI) are controlled by the volume ratio of the two homopolymers in the film. Structural and optical characterizations, as well as comparison to modeled optical properties, confirm that porous films fabricated from polymer blends deposited by RIR‐MAPLE behave as effective media over most of the visible spectrum. While evidence for the partial collapse of the porous polymer networks is observed, the RI of the porous films is reduced from that of the bulk material. Importantly, these studies demonstrate that RIR‐MAPLE should enable broadband, omnidirectional, polymeric AR coatings appropriate for flexible substrates. image

Origins of nanostructure in amorphous polymer coatings via matrix assisted pulsed laser evaporation

We investigate the nanostructure of sub-monolayer and monolayer amorphous polymer films deposited via Matrix Assisted Pulsed Laser Evaporation (MAPLE). The structure is quantified by analyzing the size distribution of polymer nanoglobules as a function of deposition parameters: time and polymer concentration. Two deposition regimes are observed in the early stages of MAPLE deposition, with a transition at a critical time. The observed distribution of nanoglobule sizes that is present after the critical time agrees well with prior molecular dynamics simulations of the MAPLE process. We discuss the mechanism of nanostructured coatings within the framework of the Zhigilei model.

Active protein and calcium hydroxyapatite bilayers grown by laser techniques for therapeutic applications

Active protein and bioceramic calcium hydroxyapatite (HA) bilayers were grown by combining conventional pulsed laser deposition (PLD) and matrix-assisted pulsed laser evaporation (MAPLE) techniques. A pulsed UV KrF* excimer laser was used for the irradiations. The HA layers were grown by PLD. Proteins with antimicrobial action were attached to the bioceramic layers using MAPLE. The composite MAPLE targets were obtained by dissolving the proteins powder in distilled water. The crystalline status and chemical composition of the obtained structures were studied by X-ray diffractometry and Fourier transform infrared spectroscopy. The layers were grown for the design of advanced future metal implants coatings, ensuring both enhanced bone formation and localized antimicrobial therapy. Our results demonstrated that protein coatings improve bone cell proliferation in vitro. Immunofluorescence experiments show that actin filaments stretch throughout bone cells and sustain their optimal spreading.

MAPLE-based method to obtain biodegradable hybrid polymeric thin films with embedded antitumoral agents

In this work, antitumor compounds, lactoferrin [recombinant iron-free (Apo-rLf)], cisplatin (Cis) or their combination were embedded within a biodegradable polycaprolactone (PCL) polymer thin film, by a modified approach of a laser-based technique, matrix-assisted pulsed laser evaporation (MAPLE). The structural and morphological properties of the deposited hybrid films were analyzed by Fourier-transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). The in vitro effect on the cells' morphology and proliferation of murine melanoma B16-F10 cells was investigated and correlated with the films' surface chemistry and topography. Biological assays revealed decreased viability and proliferation, lower adherence, and morphological modifications in the case of melanoma cells cultured on both Apo-rLf and Cis thin films. The antitumor effect was enhanced by deposition of Apo-rLf with Cis within the same film. The unique capability of the new approach, based on MAPLE, to embed antitumor active factors within a biodegradable matrix for obtaining novel biodegradable hybrid platform with increased antitumor efficiency has been demonstrated.

Effect of laser radiation on multi-wall carbon nanotubes: study of shell structure and immobilization process

Multi-wall carbon nanotubes (MWCNTs) with diameters between 10 and 15 nm were transferred and immobilized onto SiO2 glass substrates by ultraviolet matrix assisted pulsed laser evaporation (UV-MAPLE). Toluene was chosen as solvent material for the preparation of the composite MAPLE targets. An UV KrF* (λ = 248 nm, τ FWHM ≅ 25 ns, ν = 10 Hz) excimer laser source was used for the irradiation experiments. The effects of incident laser fluence on the structure of the laser transferred MWCNTs was investigated by high resolution transmission electron microscopy and Raman spectroscopy. The surface morphology of the laser processed MWCNTs was investigated by field emission scanning electron microscopy and atomic force microscopy in acoustic (dynamic) configuration. Network-like structures constituted by individual nanotubes and nanotube bundles were created onto solid substrates. Changes in the nanotubes’ shell structure can be induced through the tuning of the laser fluence value incident onto the composite MAPLE targets.

Crystallization and natural aging of thin films produced by pulsed laser evaporation of rhenium

Crystallization and natural aging of thin films produced by pulsed laser evaporation of rhenium

Layered double hydroxides/polymer thin films grown by matrix assisted pulsed laser evaporation

Due to their highly tunable properties, layered double hydroxides (LDHs) are an emerging class of the favorably layered crystals used for the preparation of multifunctional polymer/layered crystal nanocomposites. In contrast to cationic clay materials with negatively charge layers, LDHs are the only host lattices with positively charged layers (brucite-like), with interlayer exchangeable anions and intercalated water.In this work, the deposition of thin films of Mg and Al based LDH/polymers nanocomposites by laser techniques is reported. Matrix assisted pulsed laser evaporation was the method used for thin films deposition. The Mg–Al LDHs capability to act as a host for polymers and to produce hybrid LDH/polymer films has been investigated. Polyethylene glycol with different molecular mass compositions and ethylene glycol were used as polymers. The structure and surface morphology of the deposited LDH/polymers films were examined by X-ray diffraction, Fourier transform infra-red spectroscopy, atomic force microscopy and scanning electron microscopy.

Protein-resistant polymer coatings obtained by matrix assisted pulsed laser evaporation

Adsorption of proteins and polysaccharides is known to facilitate microbial attachment and subsequent formation of biofilm on surfaces that ultimately results in its biofouling. Therefore, protein repellent modified surfaces are necessary to block the irreversible attachment of microorganisms. Within this context, the feasibility of using the Poly(ethylene glycol)-block-poly(ɛ-caprolactone) methyl ether (PEG-block-PCL Me) copolymer as potential protein-resistant coating was explored in this work. The films were deposited using Matrix Assisted Pulsed Laser Evaporation (MAPLE), a technique that allows good control of composition, thickness and homogeneity. The chemical and morphological characteristics of the films were examined using Fourier Transform Infrared Spectroscopy (FTIR), contact angle measurements and Atomic Force Microscopy (AFM). The FTIR data demonstrates that the functional groups in the MAPLE-deposited films remain intact, especially for fluences below 0.5Jcm−2. Optical Microscopy and AFM images show that the homogeneity and the roughness of the coatings are related to both laser parameters (fluence, number of pulses) and target composition. Protein adsorption tests were performed on the PEG-block-PCL Me copolymer coated glass and on bare glass surface as a control. The results show that the presence of copolymer as coating significantly reduces the adsorption of proteins.

MAPLE Deposition of Macromolecules

AbstractMacromolecules are poised to feature prominently as components in organic electronics, medical implants, drug delivery systems, and sensors. A common theme for the role polymers will play in all of these is as a thin film. In all applications, it is paramount to have precise control over film thickness, structure, morphology, surfaces roughness, etc. Here, matrix‐assisted pulsed laser evaporation (MAPLE) is reviewed as a route to processing polymer and other soft matter thin films with control over the above‐mentioned parameters. After briefly discussing the experimental setup and current proposed mechanism of film formation via MAPLE, the use of MAPLE to process thin films is highlighted for use in various technologies and applications. Future directions and challenges for MAPLE processing of thin films are also discussed.magnified image

Mass-selected photodissociation studies of AlPbn+clusters (n =7–16): Evidence for the extraordinary stability of AlPb10+and AlPb12+

We report fragmentation pathways and dissociation energies of AlPb${}_{n}^{+}$ ($n=7$--16) clusters. The clusters are produced with pulsed laser vaporization and studied in a supersonic molecular beam setup. They are mass selected and photodissociated with 532 and 355 nm laser light. Photofragments are thereafter mass separated in a tandem reflectron time-of-flight mass spectrometer. Bare Pb${}_{n}^{+}$ ($n$ $=$ 8--16) clusters preferentially evaporate Pb atoms, with the exception of Pb${}_{15}^{+}$ that fragments by loss of a Pb${}_{2}$ dimer to form the stable Pb${}_{13}^{+}$ cluster. The smallest AlPb${}_{n}^{+}$ ($n$ $=$ 7--11) clusters also show mainly atomic Pb evaporation, whereas the favored fragmentation pathway of the larger clusters ($n$ $=$ 12--16) involves Pb${}_{2}$ and Pb${}_{3}$ fragments. AlPb${}_{10}^{+}$ and AlPb${}_{12}^{+}$ are the most intense fragments of several larger cluster sizes, demonstrating the high stability of these two sizes. Dissociation energies corresponding to the most facile fragmentation channel of AlPb${}_{n}^{+}$ ($n$ $=$ 11--15) are bracketed from the measured laser fluence dependencies of the fragment intensities using constraints imposed by unimolecular reaction rates.

Photofragmentation of mass-selected vanadium doped cobalt cluster cations

The stability of mass-selected vanadium doped cobalt cluster cations (Co n−1V+, n = 11–21 and Co13−m V m +, m = 0–3) is studied by photofragmentation. The clusters are produced by pulsed laser vaporization, mass-separated in a dual reflectron time-of-flight mass spectrometer, and photodissociated using the second harmonic of a Nd:YAG laser. The recorded fragmentation spectra show that all studied clusters prefer dissociation by loss of a cobalt atom. Sequential cobalt atom evaporation is found at higher laser fluences. No dissociation channel involving vanadium loss is observed, consistent with the V-Co bonds being stronger than the Co-Co bonds. Co12V+, which was predicted to have an icosahedral symmetry, is found to be the most stable cluster among the singly vanadium doped species. Consecutive increment of the vanadium concentration along the Co13 − m V m + (m = 0–3) series further confirms the enhanced stability of Co12V+, in excellent agreement with theoretical predictions [S. Datta, M. Kabir, T. Saha-Dasgupta, A. Mookerjee, Phys. Rev. B 80, 085418 (2009)].

Antimicrobial activity of biopolymer–antibiotic thin films fabricated by advanced pulsed laser methods

We report on thin film deposition by matrix assisted pulsed laser evaporation (MAPLE) of two polymer–drug composite thin film systems. A pulsed KrF* excimer laser source (λ=248nm, τ=25ns, ν=10Hz) was used to deposit composite thin films of poly(d,l-lactide) (PDLLA) containing several gentamicin concentrations. FTIR spectroscopy was used to demonstrate that MAPLE-transferred materials exhibited chemical structures similar to those of drop cast materials. Scanning electron microscopy data indicated that MAPLE may be used to fabricate thin films of good morphological quality. The activity of PDLLA–gentamicin composite thin films against Staphylococcus aureus bacteria was demonstrated using drop testing. The influence of drug concentration on microbial viability was also assessed. Our studies indicate that polymer–drug composite thin films prepared by MAPLE may be used to impart antimicrobial activity to implants, medical devices, and other contact surfaces.

Functionalized porphyrin conjugate thin films deposited by matrix assisted pulsed laser evaporation

We report on the deposition of nanostructured porphyrin-base, 5(4-carboxyphenyl)-10,15,20-tris(4-phenoxyphenyl)-porphyrin thin films by matrix assisted pulsed laser evaporation onto silicon substrates with screen-printed electrodes. AFM investigations have shown that at 400mJ/cm2 fluence a topographical transition takes place from the platelet-like stacking porphyrin-based nanostructures in a perpendicular arrangement to a quasi-parallel one both relative to the substrate surface. Raman spectroscopy has shown that the chemical structure of the deposited thin films is preserved for fluences within the range of 200–300mJ/cm2. Cyclic voltammograms have demonstrated that the free porphyrin is appropriate as a single mediator for glucose in a specific case of screen-printed electrodes, suggesting potential for designing a new class of biosensors.

Characterization of Colloidal Quantum Dot Ligand Exchange by X-ray Photoelectron Spectroscopy

Colloidal quantum dots (CQDs) are chemically synthesized semiconductor nanoparticles with size-dependent wavelength tunability. Chemical synthesis of CQDs involves the attachment of long organic surface ligands to prevent aggregation; however, these ligands also impede charge transport. Therefore, it is beneficial to exchange longer surface ligands for shorter ones for optoelectronic devices. Typical characterization techniques used to analyze surface ligand exchange include Fourier-transform infrared spectroscopy, x-ray diffraction, transmission electron microscopy, and nuclear magnetic resonance spectroscopy, yet these techniques do not provide a simultaneously direct, quantitative, and sensitive method for evaluating surface ligands on CQDs. In contrast, x-ray photoelectron spectroscopy (XPS) can provide nanoscale sensitivity for quantitative analysis of CQD surface ligand exchange. A unique aspect of this work is that a fingerprint is identified for shorter surface ligands by resolving the regional XPS spectrum corresponding to different types of carbon bonds. In addition, a deposition technique known as resonant infrared matrix-assisted pulsed laser evaporation is used to improve the CQD film uniformity such that stronger XPS signals are obtained, enabling more accurate analysis of the ligand exchange process.

Processing and immobilization of chondroitin-4-sulphate by UV laser radiation

Chondroitin-4-sulphate (ChS A) was immobilized by matrix assisted pulsed laser evaporation (MAPLE) with the aid of a UV KrF* excimer laser source. Distilled water was used as solvent for the preparation of the frozen composite MAPLE targets. The surface morphology, chemical structure and functional properties of laser transferred ChS A were investigated as a function of laser processing conditions. The results indicate that the amount of laser immobilized material, structure, and functional properties can be controlled by the laser fluence value used for the irradiation of the MAPLE targets. Under selected irradiation conditions besides the molecular structure, the functional properties of the laser processed ChS A molecules can be maintained.

Functionalized magnetite silica thin films fabricated by MAPLE with antibiofilm properties

We report on the fabrication of magnetite/salicylic acid/silica shell/antibiotics (Fe3O4/SA/SiO2/ATB) thin films by matrix-assisted pulsed laser evaporation (MAPLE) to inert substrates. Fe3O4-based powder have been synthesized and investigated by XRD and TEM. All thin films were studied by FTIR, SEM and in vitro biological assays using Staphylococcus aureus and Pseudomonas aeruginosa reference strains, as well as eukaryotic HEp-2 cells. The influence of the obtained nanosystems on the microbial biofilm development as well as their biocompatibility has been assessed. For optimum deposition conditions, we obtained uniform adherent films with the composition identical with the raw materials. Fe3O4/SA/SiO2/ATB thin films had an inhibitory activity on the ability of microbial strains to initiate and develop mature biofilms, in a strain- and antibiotic-dependent manner. These magnetite silica thin films are promising candidates for the development of novel materials designed for the inhibition of medical biofilms formed by different pathogenic agents on common substrates, frequently implicated in the etiology of chronic and hard to treat infections.

Combinatorial matrix-assisted pulsed laser evaporation: Single-step synthesis of biopolymer compositional gradient thin film assemblies

We introduce a combinatorial approach for the fabrication of organic biopolymer thin films. Structures with compositional gradient are obtained by simultaneous laser vaporization of two distinct targets. Matrix-assisted pulsed laser evaporation deposition method was applied to obtain a compositional library of levan and oxidized levan in form of thin film. The gradient of film composition and structure was demonstrated by infrared spectroscopy while in vitro cell culture assays illustrated characteristic responses of cells to specific surface regions. The method can rapidly generate discrete areas of organic film compositions with improved properties than starting materials.

Functionalized ormosil scaffolds processed by direct laser polymerization for application in tissue engineering

Synthesized N,N′-(methacryloyloxyethyl triehtoxy silyl propyl carbamoyl-oxyhexyl)-urea hybrid methacrylate was polymerized by direct laser polymerization using femtosecond laser pulses with the aim of using it for subsequent applications in tissue engineering. The as-obtained scaffolds were modified either by low pressure argon plasma treatment or by covering the structures with two different proteins (lysozyme, fibrinogen). For improved adhesion, the proteins were deposited by matrix assisted pulsed laser evaporation technique. The functionalized structures were tested in mouse fibroblasts culture and the cells morphology, proliferation, and attachment were analyzed.